The primary purpose of these studies has been to evaluate the mechanisms whereby stimuli from the peripheral and central chemoreceptors are integrated within the brainstem. Processes which may be responsible for the neurogenesis of various respiratory patterns have also been examined. We have found that brainstem respiratory units respond differently to stimuli acting at the peripheral chemoreceptors as compared to central chemoreceptor stimulation. In contrast, stimulation of either chemoreceptor site produced identical alterations in the activity of phrenic motoneurons. The conclusions drawn were two-fold: 1. There is a differential integration of peripheral and central chemoreceptor stimuli within the brainstem; 2. There is a significant filtration and integration of activity from brainstem respiratory centers at the phrenic motonucleus. In other studies, we have demonstrated that the gasping respiratory activity which is generated by the medullary brainstem is fundamentally different from eupnea. Thus, gasping, in contrast to eupnea, is not systematically altered by stimulation of the peripheral or central chemoreceptors. Moreover, the pattern of phrenic nerve activity, and of single fibers comprising this activity, differ substantially between eupnea and gasping. These results imply that a unitary process may not be responsible for the generation of all types of rhythmic respiratory activity.